As a rule, machine tools or machining centers comprise a clamping device that is integrated into their work spindle for automatically clamping and disengaging machining tools. In the clamping devices known in the art, the machining tools are held by a clamping assembly which is disposed in the work spindle on the forward end of a tension rod that is biased by a spring assembly. As a rule, the clamping assembly comprises a plurality of radially movable pincer members by means of which the machining tool is drawn into the work spindle. To release the machining tools, the tension rod is moved against the force of the spring assembly using a so-called releasing unit so that the clamping assembly with the pincer members is opened and releases the machining tool.
A clamping device of this type is known from DE 10 2004 051 031 B3. In this clamping device, the spring assembly is configured in the form of a cup spring pack with a plurality of cup springs disposed adjacent to one another. However, cup spring packs of this type have a relatively high weight and, in addition, because of the high loads to which they are subjected, only a limited service life. In addition, the installation of such cup spring packs is associated with considerable expenditure of labor. Furthermore, this may give rise to the problem that the individual cup springs are subjected to different loads.